Cable fault diagnosis method and system based on semi-conductive resistance water buffer strip ablation gas

Abstract

The invention discloses a cable fault diagnosis method and system based on ablation gas of a semi-conductive resistance water buffer zone, and the method comprises the steps: extracting gas in a to-be-detected cable buffer layer through a gas collection assembly disposed outside a main insulation part of a cable body; analyzing the gas in the buffer layer of the to-be-detected cable through a cable characteristic gas analysis instrument to obtain the concentrations of hydrogen and propane in the buffer layer of the to-be-detected cable; and comparing the hydrogen concentration with the hydrogen concentration of the cable in a normal operation state, and determining the operation state of the cable to be detected according to the propane content. The problem that the detection time is interfered or missed in the prior art is solved, and whether the semi-conductive resistance water buffer strip is ablated or not can be rapidly and accurately detected and judged.

Description

Technical Field

[0001] The invention relates to the technical field of monitoring and identifying ablation characteristic gases of a semiconductor resistive water buffer zone, and in particular to a cable fault diagnosis method and system based on ablation gases of a semiconductor resistive water buffer zone. Background Art

[0002] Semiconducting water-blocking buffer strips are the basic materials that constitute the buffer layer of high-voltage cables. In recent years, corrugated aluminum sheathed XLPE cables with voltage levels of 110kV and above in many places have experienced failures caused by the ablation of the water-blocking buffer layer. The ablation failure of the semiconducting water-blocking buffer strip in the cable buffer layer has the characteristics of high voltage level, great harm, strong suddenness and relatively hidden. Most of the faulty cables have been in operation for less than 10 years and are in a stable operation period. They will not attract much attention before the failure occurs. Therefore, a feasible solution is urgently needed to accurately detect the ablation failure of the semiconducting water-blocking buffer strip.

[0003] At present, studies have found that semiconductor water buffer strips will produce specific gas products when ablation failure occurs. Zhao Xiyuan of Xi'an Jiaotong University conducted a simulation experiment on the ablation of semiconductor water buffer strips and found that the buffer layer will produce hydrogen with sharp characteristics when it is ablated under humid conditions. Zhou Kai and others from Sichuan University concluded through a simulation experiment on the ablation of semiconductor water buffer strips that the stages of cable buffer layer failure can be divided into corrosion stage and ablation stage. In the corrosion stage, the buffer layer will release a large amount of H2, while in the ablation stage, CH4, C2H6, C2H4 and C2H2 gases will be produced. Liu Shunman and others conducted a simulation experiment on the ablation of the buffer layer under the needle-plate discharge model and found that the semiconductor water buffer strip will produce aromatic hydrocarbon gases such as toluene and ethylene dibutyl phthalate under the action of severe arc burning.

[0004] The existing detection methods for high-voltage cable buffer layer ablation faults mainly include partial discharge method, X-ray detection technology, and characteristic gas product detection method.

[0005] The basic principle of local electrical detection is to monitor the operating status of the cable body by detecting the characteristic physical signals generated by abnormal discharge in the cable. According to the different monitoring objects, it can be divided into non-electrical quantity monitoring method and electrical quantity monitoring method. The non-electrical quantity monitoring method mainly includes ultrasonic method, and the electrical quantity monitoring method includes pulse current method, electromagnetic coupling method, differential method, etc. The disadvantage of this method is that when the discharge ablation of the buffer layer does not destroy the main insulation, the local discharge signal caused is very small and difficult to detect. In the actual application process, it will be interfered by noise and there is a possibility of missing the discharge signal.

[0006] X-ray detection uses lasers to obtain the internal conditions of the buffer layer of high-voltage cables, and obtains patterns from X-rays to identify defects in the buffer layer. Liu Sanwei and other scholars detected white spots and ablation defects in the buffer layer through X-ray detection and processing of detection images through convolutional neural networks and fully convolutional neural networks. X-ray detection also has the problem of requiring multiple adjustments to the radiation source and flat-panel detector angles, causing harm to the human body, and the equipment is less portable, which cannot meet the needs of large-scale detection in power systems.

[0007] The defect detection technology based on characteristic gas product analysis utilizes the characteristic gas generated when a fault occurs in the currently existing power equipment (including cable inflation / extraction components, cable characteristic gas analyzers). When the characteristic gas of a specific fault or the characteristic quantity composed of gas type and concentration is identified, the power equipment can be diagnosed to have such a fault, and it can effectively diagnose whether the cable has a semiconductor resistance water buffer zone ablation defect. Summary of the invention

[0008] The present invention aims at the shortcomings of the existing partial discharge detection method, such as the small partial discharge signal, easy to be interfered by noise, and easy to miss the discharge signal when the discharge ablation of the buffer layer does not damage the main insulation, and the shortcomings of the X-ray detection method, such as the inconvenience of equipment adjustment and damage to the human body. A cable fault diagnosis method and system based on semiconductor resistance water buffer zone ablation gas is provided, the method comprising:

[0009] The gas in the buffer layer of the cable to be tested is extracted through the gas extraction component installed outside the main insulation of the cable body;

[0010] Analyzing the gas in the buffer layer of the cable to be tested by a cable characteristic gas analyzer to obtain the concentrations of hydrogen and propane in the buffer layer of the cable to be tested;

[0011] The hydrogen concentration is compared with the hydrogen concentration under normal operation of the cable, and the operation state of the cable to be tested is determined according to the propane content.

[0012] Furthermore, the air extraction assembly is installed on the outside of the cable and communicated with the inside of the cable buffer layer, so as to realize the inflation or extraction of air in the buffer layer without stopping the cable and without damaging the main insulation of the cable.

[0013] Furthermore, the air extraction assembly is installed at a key location for detecting and troubleshooting the cable through a limited-position punching method, and the punching interval is selected according to actual needs and installation costs.

[0014] Furthermore, the cable characteristic gas analysis instrument integrates a microcontroller, an air pump, an exhaust hose and a two-dimensional gas sensor.

[0015] Further, the hydrogen concentration is compared with the hydrogen concentration under normal operation of the cable, and the operation state of the cable to be tested is determined according to the propane content, including:

[0016] Assume that when the cable is in normal operation, the concentration of hydrogen is α0, and the concentrations of hydrogen and propane in the buffer layer of the cable to be tested are α1 and β1 respectively;

[0017] α1-α0 ×100%<10%

[0018] When the increment of α1 relative to α0 is α0, and β1=0, it is determined that the operating state of the cable to be tested is normal;

[0019] α1-α0 ×100%>10%

[0020] When the increment of α1 relative to α0 is α0, and β1=0, the cable under test is in a state of severe moisture, and the operating state of the cable under test is determined to be a warning state;

[0021] α1-α0 ×100%>10%

[0022] When the increment of α1 relative to α0 is α0, and β1>0, the cable under test is seriously damp and a buffer layer ablation failure has occurred, and the operating state of the cable under test is determined to be a fault state.

[0023] The present invention also provides a cable fault diagnosis system based on a semiconductor resistor water buffer zone ablative gas, comprising:

[0024] A gas extraction module is used to extract the gas in the buffer layer of the cable to be tested through a gas extraction component installed outside the main insulation of the cable body;

[0025] A gas concentration acquisition module, used to analyze the gas in the buffer layer of the cable to be tested by a cable characteristic gas analysis instrument to obtain the concentrations of hydrogen and propane in the buffer layer of the cable to be tested;

[0026] The cable status judgment module is used to compare the hydrogen concentration with the hydrogen concentration under the normal operation state of the cable, and determine the operation state of the cable to be tested according to the propane content.

[0027] Furthermore, the air extraction assembly is installed on the outside of the cable and communicated with the inside of the cable buffer layer, so as to realize the inflation or extraction of air in the buffer layer without stopping the cable and without damaging the main insulation of the cable.

[0028] Furthermore, the air extraction assembly is installed at a key location for detecting and troubleshooting the cable through a limited-position punching method, and the punching interval is selected according to actual needs and installation costs.

[0029] Furthermore, the cable characteristic gas analysis instrument integrates a microcontroller, an air pump, an exhaust hose and a two-dimensional gas sensor.

[0030] Furthermore, the cable status judgment module includes:

[0031] The gas concentration determination submodule is used to assume that under normal cable operation, the concentration of hydrogen is α0, and the concentrations of hydrogen and propane in the buffer layer of the cable to be tested are α1 and β1 respectively;

[0032] α1-α0 ×100%<10%

[0033] A first state determination submodule, used for determining that the operating state of the cable to be tested is a normal state when the increment of α1 relative to α0 is α0 and β1=0;

[0034] The second state determination submodule is used when the increment of α1 relative to α0 is When β1=0, the cable under test is in a state of severe moisture, and the operating state of the cable under test is determined to be a warning state;

[0035] The third state determination submodule is used when the increment of α1 relative to α0 is When β1>0, the cable under test is seriously damp and a buffer layer ablation failure has occurred, and it is determined that the operating state of the cable under test is a fault state.

[0036] The present invention provides a cable fault diagnosis method and system based on ablative gas in a semiconductor resistive water buffer zone. The cable buffer layer gas filling and air extraction components are installed using the existing limit punching technology. The detection can be performed without damaging the cable insulation body or stopping the cable. A portable integrated device can be used to accurately, quickly, conveniently and flexibly detect the operating status of the cable to be tested, and timely discover the safety hazards of cable operation and faulty cables. Cable fault detection and cable replacement indication can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a flow chart of a cable fault diagnosis method based on a semiconductor resistance water buffer zone ablative gas provided by an embodiment of the present invention;

[0038] Figure 2 is the concentration of propane or other gases in the buffer layer of the cable buffer layer ablation fault involved in the embodiment of the present invention;

[0039] Figure 3 is the concentration of hydrogen and other gases in the buffer layer of the cable buffer layer ablation fault involved in the embodiment of the present invention;

[0040] Figure 4The concentration of inorganic gases such as hydrogen involved in the embodiment of the present invention changes during the cable ablation process;

[0041] Figure 5 The propane concentration involved in the embodiment of the present invention varies with the cable ablation process;

[0042] Figure 6 is a cable fault judgment flow chart involved in an embodiment of the present invention;

[0043] Figure 7 It is a schematic diagram of an implementation of a cable fault assessment and diagnosis method according to an embodiment of the present invention;

[0044] Figure 8 It is a structural schematic diagram of a cable fault diagnosis system based on a semiconductor resistive water buffer zone ablative gas according to an embodiment of the present invention. DETAILED DESCRIPTION

[0045] Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention, so the present invention is not limited to the specific implementation disclosed below.

[0046] Example 1

[0047] The present invention provides a method for evaluating and diagnosing buffer layer ablation faults based on the characteristic gases propane and hydrogen produced when a semiconductor resistive water buffer zone ablation faults occur. The method can extract buffer layer gas and perform gas analysis on operating cables suspected of having buffer layer ablation defects. The cable with a gas extraction component installed can be subjected to real-time gas extraction and analysis as a basis for determining the operating status of the cable. Existing studies have shown that the airtightness inside the cable buffer layer allows the characteristic gases produced by ablation of various cable structures to diffuse and be stored in the buffer layer. The present invention is based on the results of gas chromatography analysis of gas production in stages in a buffer layer simulation ablation experiment. The gas chromatograph analysis results are as follows: Figure 2 , 3 The experiment found that the concentration of hydrogen in the buffer layer gas gradually increased with the increase of ablation time, while propane was not produced at the beginning of ablation. As the ablation time accumulated, propane was gradually generated and its concentration gradually increased. The concentration changes of hydrogen and propane are shown as follows: Figure 4 , 5 As shown. Based on this experimental phenomenon, the present invention proposes a method for diagnosing buffer layer ablation faults based on propane and hydrogen. Based on this experimental phenomenon, the present invention proposes a method for diagnosing cable faults based on ablation gas of a semiconductor water buffer zone, which mainly includes a gas extraction component installed outside the main insulation of the cable body, a matching cable characteristic gas analysis instrument, and an internal gas extraction component, a power supply, a microcontroller, and a gas sensor. The process is as follows Figure 1As shown, the following steps are included:

[0048] Step S101, extracting gas in the buffer layer of the cable to be tested through a gas extraction component installed outside the main insulation of the cable body.

[0049] Installing the cable gas extraction and inflation component on the cable body can extract the gas in the cable buffer layer and ensure that the normal operation of the cable is not affected. The gas extraction component is installed on the outside of the cable and connected to the inside of the cable buffer layer to achieve inflation or extraction of gas in the buffer layer without stopping the cable and without damaging the main insulation of the cable. The gas extraction component is installed at the key detection and troubleshooting location of the cable through the limited punching method, and the punching interval is selected according to actual needs and installation costs.

[0050] Step S102, analyzing the gas in the buffer layer of the cable to be tested by a cable characteristic gas analyzer to obtain the concentrations of hydrogen and propane in the buffer layer of the cable to be tested. Using a gas analyzer that integrates a microcontroller, an air pump, an exhaust hose, and a two-dimensional gas sensor, the buffer layer gas of the target cable is extracted and analyzed to provide the operating status of the cable.

[0051] Step S103, comparing the hydrogen concentration with the hydrogen concentration under normal operation of the cable, and determining the operation state of the cable to be tested according to the propane content.

[0052] Assume that the concentration of hydrogen is α0 under normal operation of the cable, where α0 is the empirical value obtained through actual operation and testing of the cable. Under the same working conditions, the concentrations of hydrogen and propane in the buffer layer of the cable to be tested are collected and analyzed by the gas analyzer, and are α1 and β1 respectively; by analyzing the collected α1 and β1 and comparing them with α0, it is possible to determine what type of fault the cable has.

[0053] When the increment of α1 relative to α0 is When β1=0, it is determined that the operating state of the cable to be tested is normal;

[0054] When the increment of α1 relative to α0 is When β1=0, the cable under test is in a state of severe moisture, and the operating state of the cable under test is determined to be a warning state;

[0055] When the increment of α1 relative to α0 is When β1>0, the cable under test is seriously damp and the buffer layer has been burned, and the operating state of the cable under test is determined to be a fault state. At this time, the cable should be stopped immediately and replaced. The judgment method flow chart is as follows Figure 6 Shown

[0056] Example 2

[0057] See also Figure 7 During the implementation of the cable fault assessment and diagnosis method, the device for realizing the electricity fee fault diagnosis includes a cable inflation / gas extraction component 1, a characteristic gas analysis instrument, including an air pump 2, a propane and hydrogen sensor 3, a microcontroller and a display module 4. The cable inflation / gas extraction component 1 is installed on the cable body, and the air pump 2, the propane and hydrogen sensor 3, the microcontroller and the display module 4 are integrated inside a cable characteristic gas analysis device. It can realize the extraction of buffer layer gas and gas analysis of the running cable. It has the advantages of portable equipment, simple operation, no need to shut down the cable and harmless to the human body. The specific steps of the invention application are as follows:

[0058] A limited punching method is proposed for the cable live inflation\gas extraction metal components without damaging the buffer layer and internal structure. The maximum gas extraction rate is 50L / min, meeting the 25kV DC withstand voltage for 3min, and the IP protection level reaches IP68.

[0059] The cable characteristic gas analysis instrument includes a gas extraction hose, an air pump, a gas sensor, a display module, and a microcontroller, which can realize the integration and portability of the detection instrument.

[0060] The cable live gas charging / gas extraction metal component is installed on the outside of the cable and connected to the cable buffer layer, which can realize the gas charging / gas extraction in the buffer layer without stopping the cable and without damaging the main insulation of the cable. The gas sensor of the cable characteristic gas analyzer adopts a metal oxide electrochemical sensor, which is installed in the closed air cavity inside the instrument to reduce the measurement error, and its measurement accuracy can meet the requirements of the present invention.

[0061] The cable buffer layer has good air tightness, and the key information of characteristic gases generated by failures at various stages and parts of the cable are diffused and stored in the buffer layer.

[0062] The air pump inside the cable characteristic gas analyzer used in the present invention is a 12V micro DC air pump with an air pumping flow rate of at least 10L / min, a power of about 12W, and a weight of only about 300g.

[0063] The cable characteristic gas analyzer has an internal rechargeable power supply with a capacity of approximately 20,000 mA, which can achieve outdoor endurance operation.

[0064] The cable limit drilling and air extraction components are installed in the position section where the cable needs to be inspected and troubleshooted during operation in the power system, and the drilling interval is selected according to actual needs and installation costs.

[0065] When the cable is in normal operation, the concentration of hydrogen is α0, where α0 is an empirical value obtained through actual cable operation and testing.

[0066] The hydrogen concentration inside the buffer layer of the cable to be tested is measured by the instrument as α1, and the relationship between the concentration α1 and the concentration α0 is determined to determine whether the cable to be tested is operating normally.

[0067] The propane concentration inside the buffer layer of the cable to be tested is measured by the instrument as β1, which needs to be further analyzed in conjunction with the aforementioned hydrogen concentration α1.

[0068] The present invention calculates the incremental percentage of hydrogen concentration in the buffer layer as follows:

[0069] In order to reduce the error caused by the operating conditions, the invention sets a percentage threshold of 10% for the increment of α1 and α0. If this threshold is exceeded, it is judged that the concentration of hydrogen exceeds the normal operating level and the cable is seriously damp.

[0070] If the percentage of the increment of α1 and α0 is within 10%, there is no ablation fault in the cable buffer layer, and the cable is judged to be operating safely and stably. At this time, the cable is in normal operation.

[0071] If the percentage of the increments of α1 and α0 exceeds the threshold value of 10%, the cable buffer layer has been seriously dampened. At this time, combined with the propane gas concentration, there are two cases.

[0072] If the propane concentration β1 = 0, the cable is only seriously damped, and the buffer layer does not burn out. The electrical properties of the buffer layer, such as resistivity, have changed due to dampness, and the probability of burning out has greatly increased. At this time, the cable is in a warning state.

[0073] If the propane concentration β1>0, the cable is seriously damp and has ablation failure, and the buffer layer has characteristic gas that determines the ablation failure of the cable. At this time, the operation state of the cable is a faulty operation state.

[0074] If the cable is judged to be in a faulty operating state, the main insulation inside the cable has been partially damaged. It is necessary to shut down the cable and replace the operating cable as soon as possible to avoid further expansion of the fault and endanger the operation of the power grid.

[0075] Example 3

[0076] Based on the same inventive concept, the present invention also provides a cable fault diagnosis system based on a semiconductor resistor water buffer zone ablative gas, such as Figure 8 As shown, including:

[0077] The gas extraction module 810 is used to extract the gas in the buffer layer of the cable to be tested through a gas extraction component installed outside the main insulation of the cable body;

[0078] The gas concentration acquisition module 820 is used to analyze the gas in the buffer layer of the cable to be tested by a cable characteristic gas analysis instrument to obtain the concentration of hydrogen and propane in the buffer layer of the cable to be tested;

[0079] The cable status judgment module 830 is used to compare the hydrogen concentration with the hydrogen concentration under the normal operation state of the cable, and determine the operation state of the cable to be tested according to the propane content.

[0080] Furthermore, the air extraction assembly is installed on the outside of the cable and communicated with the inside of the cable buffer layer, so as to realize the inflation or extraction of air in the buffer layer without stopping the cable and without damaging the main insulation of the cable.

[0081] Furthermore, the air extraction assembly is installed at a key location for detecting and troubleshooting the cable through a limited-position punching method, and the punching interval is selected according to actual needs and installation costs.

[0082] Furthermore, the cable characteristic gas analysis instrument integrates a microcontroller, an air pump, an exhaust hose and a two-dimensional gas sensor.

[0083] Furthermore, the cable status judgment module includes:

[0084] The gas concentration determination submodule is used to assume that under normal cable operation, the concentration of hydrogen is α0, and the concentrations of hydrogen and propane in the buffer layer of the cable to be tested are α1 and β1 respectively;

[0085] The first state determination submodule is used when the increment of α1 relative to α0 is When β1=0, it is determined that the operating state of the cable to be tested is normal;

[0086] The second state determination submodule is used when the increment of α1 relative to α0 is When β1=0, the cable under test is in a state of severe moisture, and the operating state of the cable under test is determined to be a warning state;

[0087] The third state determination submodule is used when the increment of α1 relative to α0 is When β1>0, the cable under test is seriously damp and a buffer layer ablation failure has occurred, and it is determined that the operating state of the cable under test is a fault state.

[0088] The present invention provides a cable fault diagnosis method and system based on ablative gas in a semiconductor resistive water buffer zone, which can identify and detect cable buffer layer ablation faults, and the main effects achieved are: (1) The cable buffer layer inflation and air extraction components are installed using existing limit punching technology, and the detection can be performed without damaging the cable insulation body or shutting down the cable. (2) A portable integrated device can be used to accurately, quickly, conveniently, and flexibly detect the operating status of the cable to be tested, and timely discover safety hazards and faulty cables in cable operation. Cable fault detection and cable replacement instructions can be achieved.

[0089] Compared with the prior art, the advantages of the present invention are as follows:

[0090] (1) Compared with the existing partial discharge detection technology and X-ray detection technology, the technology adopted by the present invention uses a portable device with a simpler structure, lighter weight, smaller size, lower equipment loss, and easy use, which can realize the portability of the detection equipment.

[0091] (2) The present invention only requires the use of an existing cable buffer layer inflation and air extraction assembly and a portable device, and a device that does not need to damage the cable or change the cable structure, and can achieve live detection of the cable to be tested without shutting down the cable.

[0092] (3) In view of the problems existing in the existing X-ray detection technology, such as the need to adjust the radiation source and the angle of the flat-panel detector multiple times, which may cause harm to the human body, the technology adopted in the present invention only requires one extraction and one detection, without any steps that may cause harm to the human body.

[0093] (4) In view of the problems in existing partial discharge detection methods, the partial discharge signal caused by partial buffer layer discharge ablation is very small (such as the discharge does not damage the main insulation) and is difficult to detect, and is easily interfered by noise and may miss the discharge signal. The present invention utilizes the characteristic gas accumulated between the buffer layers to achieve detection at any time without the possibility of missed detection.

[0094] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0095] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0096] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0097] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalents that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A cable fault diagnosis method based on ablative gas in a semi-conductive water buffer zone, characterized in that: include: The gas in the buffer layer of the cable to be tested is extracted through the gas extraction component installed outside the main insulation of the cable body; Analyzing the gas in the buffer layer of the cable to be tested by a cable characteristic gas analyzer to obtain the concentrations of hydrogen and propane in the buffer layer of the cable to be tested; The hydrogen concentration is compared with the hydrogen concentration under normal operation of the cable, and the operation state of the cable to be tested is determined according to the propane content.

2. The method according to claim 1, characterized in that The air extraction component is installed on the outside of the cable and communicated with the inside of the cable buffer layer, so as to realize the inflation or extraction of air in the buffer layer without stopping the cable and without damaging the main insulation of the cable.

3. The method according to claim 1, characterized in that The air extraction component is installed at the key detection and troubleshooting position of the cable through a limited drilling method, and the drilling interval is selected according to actual needs and installation costs.

4. The method according to claim 1, characterized in that: Cable characteristic gas analysis instrument, integrating microcontroller, gas pump, gas extraction hose and two-dimensional gas sensor.

5. The method according to claim 1, characterized in that Comparing the hydrogen concentration with the hydrogen concentration under normal operation of the cable, and determining the operating state of the cable to be tested according to the propane content, including: Assume that when the cable is in normal operation, the concentration of hydrogen is α0, and the concentrations of hydrogen and propane in the buffer layer of the cable to be tested are α1 and β1 respectively; When the increment of α1 relative to α0 is When β1=0, it is determined that the operating state of the cable to be tested is normal; When the increment of α1 relative to α0 is When β1=0, the cable under test is in a state of severe moisture, and the operating state of the cable under test is determined to be a warning state; When the increment of α1 relative to α0 is When β1>0, the cable under test is seriously damp and a buffer layer ablation failure has occurred, and it is determined that the operating state of the cable under test is a fault state.

6. A cable fault diagnosis system based on semi-conducting water buffer zone ablative gas, characterized in that: include: A gas extraction module is used to extract the gas in the buffer layer of the cable to be tested through a gas extraction component installed outside the main insulation of the cable body; A gas concentration acquisition module, used to analyze the gas in the buffer layer of the cable to be tested by a cable characteristic gas analysis instrument to obtain the concentrations of hydrogen and propane in the buffer layer of the cable to be tested; The cable status judgment module is used to compare the hydrogen concentration with the hydrogen concentration under the normal operation state of the cable, and determine the operation state of the cable to be tested according to the propane content.

7. The system according to claim 6, characterized in that The air extraction component is installed on the outside of the cable and communicated with the inside of the cable buffer layer, so as to realize the inflation or extraction of air in the buffer layer without stopping the cable and without damaging the main insulation of the cable.

8. The system according to claim 6, characterized in that The air extraction component is installed at the key detection and troubleshooting position of the cable through a limited drilling method, and the drilling interval is selected according to actual needs and installation costs.

9. The system according to claim 6, characterized in that Cable characteristic gas analysis instrument, integrating microcontroller, gas pump, gas extraction hose and two-dimensional gas sensor.

10. The system according to claim 6, characterized in that The cable status judgment module includes: The gas concentration determination submodule is used to assume that under normal cable operation, the concentration of hydrogen is α0, and the concentrations of hydrogen and propane in the buffer layer of the cable to be tested are α1 and β1 respectively; The first state determination submodule is used when the increment of α1 relative to α0 is When β1=0, it is determined that the operating state of the cable to be tested is normal; The second state determination submodule is used when the increment of α1 relative to α0 is When β1=0, the cable under test is in a state of severe moisture, and the operating state of the cable under test is determined to be a warning state; The third state determination submodule is used when the increment of α1 relative to α0 is When β1>0, the cable under test is seriously damp and a buffer layer ablation failure has occurred, and it is determined that the operating state of the cable under test is a fault state.

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